Video illustrates removal and replacement of the cooling fan in Tivo Series 3 recorder. If your ancient series 3 is making terrible sounds it is the bearing the fan which is going bad and it needs to be replaced as someday the noise will stop and so with your fan and it could damage the Series 3.
Fan I installed in Video is GDS Time Model FBA_GDT7015S12V2P2.54
https://amzn.to/3di8rpF
Weekness Tivo OEM Cooling Fans
https://www.weaknees.com/tivo-fans.php
Apvia CF7025S Fan Mentioned on Tivo Forum
https://amzn.to/3JVEXKo